210 BERGER BC AFTER POINTING

[MOTORSPORTS55]

WHAT IS THE BC OF A 210 BERGER VLD AFTER POINTING WITH WHIDDEN POINTING SYSTEM ? I NOW OUT OF THE BOX THEY ARE 0.631 AND EVEY BODY SAY YOU GAIN BC SO WQHAT IS THE NEW BC I WANTED TO SEE WHAT I WILL GAIN ON A CLICK CHART ?

THANKS SHAWN

 

[MOTORSPORTS55]

ANYONE WITH ANY INFO !!!

 

[Forum Boss]

You kind of have to work this one backwards from observations on the target. There are a lot of variables in the bullet pointing process...

1. How big are the meplats to start with?
2. How high is the BC to start with?,the pointier the bullets out of the box, the less effect pointing will have)
3. Do you uniform the meplats before/after pointing?
4. BC will also vary with velocity.

Based on recorded results with other long-range bullets, after pointing you may see a 6-18" difference in point of impact at 1000 yards compared to non-pointed bullets.

For simplicity, let's PRESUME your pointed Berger bullets impact 10" higher,a reasonable guess for starters). If I assume a 2850 fps velocity for your Berger 210s, we can plug this into ballistic software and try different BCs to see what corresponds to a 10" impact change at 1000 yards,it might be more or less, remember).

210gr Berger Claimed BC = 0.631

Drop at 1000 yards,from 100yd zero) with 2850 fps MV = 276.41"
,default 70deg F and 1000' altitude)

OK, now we need to fiddle with the BC to come up with 10" less drop at 1000 yards.,I'm using Point Blank Ballistics software, but you can do this with other programs.)

Trying different BC values, I find if I plug in 0.679 for the BC, the program says there will be 266.39" of drop,from 100yd zero) at 1000.

So this suggests pointed BC is 0.679 vs 0.631 for unpointed 210gr VLDs. That's a difference of about 0.048 BC or about 7.6%.

BUT I stress this is just guesstimation. YOU will not know how much the BC improves until you actually shoot your pointed bullets long range and measure the point of impact compared to unpointed bullets. If, for example, the diffence in impact is just 4",instead of 10"), then the change in BC is much less than 7.6%.

The reality is that you need to go out and test in the field.

 

[mikecr]

You could email Brian Litz from Berger

My best 'estimation':
If you know your SL Standard BC at xxxxfps is .631 with a meplat of .062, and you pointed it to .030, you'd be lookin at ~.680,.670-.695)

 

[Steve]

I think you would gain more accuracy by working on reload technique to get better es and sd's than what little you would gain in bc by pointing or meplat to only slightly cheat the wind better.
but that's my 2 cents.
run your load through the ballistics program but put in your bc, then add maybe 0.01 to 0.015 to the .631 and see if any gains at 1000 in the wind.

 

[mikecr]

Well I wouldn't be so sure about that.
As far as stats, BC looks to be the single biggest factor in 1KBR.
It's BC,or desire to reduce wind drift error), that put's everyone shooting heaviest per cal bullets, as hard as they can go.
It's the sole reason the 210 Berger exists..

And 10" less drift error to worry about is far more significant than any gains you'll make from a typical 1/2moa LR gun.
We're talkin 1 full MOA, less error potential.
And if you were so good with wind that you could reduce this error to 1/4moa, should you blow off this much?

 

[TonyR]

Bullet pointing and meplat trimming were discussed on the Competition Forum earlier this week.

http://www.websitetoolbox.com/tool/post/6mmbr/vpost?id=3197478

Jason Baney also wrote a great article on pointing for this site:

http://www.6mmbr.com/bulletpointer.html

Both are worth reading. I was particularly interested in Jason's observations about the variation in BC within a box of bullets by the same manufacturer. That led to a call to Whidden's, a nice long talk with John, and my purchase of both the meplat trimmer and pointing die. My results at 1000 yards prior to trimming and pointing and the subsequent improvement are very consistent with the range Jason mentions.

 

[MOTORSPORTS55]

THANKS I AM NEW TO THIS AND THIS IS A HARD QUESTION TO ANSWER !

 

[aJR]

The day they start handing out trophy's for the Highest BC on the range on Competition day i will start to believe the "Must Have BC " story .. If only hi BCs allowed you to win then the 6BR,.530 @2950fps would be at the bottom of the heap,but it isn't..For 2008 in the 10 match aggs at 1K my heavy gun shot 8.77ins for group and an average of 94 for score..I use the 187 BIB bullet with appox a .520 Bc, but you don't here me bitchin ..I know my efforts not as good as some of you guys in the states but here in Australia all the hi Bc combos have not even come close .. JR.. Jeff Rogers

 

[MOTORSPORTS55]

JR
YOU MAY BE RIGHT BUT I AM JUST TRYING TO TIGHTEN UP MY GROUP I SEEM TO ALWAYS HAVE 1 OR 2 FLYER FROM MY GROUP AT 1000 YD THAT KILL MY GROUP SIZE .

thansk shawn

 

[aJR]

Shawn, This is exactly why i returned on your post .. It is IMO far more important to have ten bullets that have the capability to stay in the group than to buck the wind like a Banshee..And when it comes to 10 times 10 as in the aggs it's even more important to have 100 from 100 bullets that are going to arrive at target with the same extreme spread that they left the muzzle at .. JR..Jeff Rogers

JR
YOU MAY BE RIGHT BUT I AM JUST TRYING TO TIGHTEN UP MY GROUP I SEEM TO ALWAYS HAVE 1 OR 2 FLYER FROM MY GROUP AT 1000 YD THAT KILL MY GROUP SIZE .

thansk shawn

 

[TonyR]

I agree with both Steve and Jeff. It would be hard to measure an improvement in BC if you have a high ES or SD. The BC is something to look at after you have single digit ES and still have more vertical than you can explain by the remaining muzzle velocity variation. The most important thing is for the bullets to arrive at the target with the same small spread as when they left the muzzle and that will only happen if the BC for all of the bullets is as close as possible regardless of what the BC is because they will loose velocity at different rates if the BCs are different. If the highest BC was the only thing that matters, the top guys in 1000 yard benchrest would all be shooting .308 240gr SMKs at 3100 fps which does not appear to be happening.
An easy way to test the effect of BC consistency for yourself without spending a lot of money on gear is to sort your bullets by tip size using a number drill gage. After reading Jason's review, I sorted a box of 100 6mm match bullets and found that the tips fell into roughly four drill sizes, drill sizes 50, 51, 52, and 53. I found that I measured most consistently if I assigned the number where the tip of the bullet just cleared the far side of the gauge. This doesn't actually measure the tip diameter but it will put bullets of the same size in the same group. Drills this size vary about .004 inches in diameter per number. I then shot groups with bullets from the same tip size and my vertical improved noticably at 300 yards compared to groups fired with unsorted bullets.

 

[Bryan Litz Ballistics]

The measured BC of the .30 cal Berger 210 VLD is:
G1 BC = 0.616 lb/in^2,average between 3000 fps and 1500 fps)
The website will be updated soon to show this,and other) updated BC's for our bullets.

I assess that pointing this bullet with John's die will increase the BC by 3.5% to 0.638 lb/in^2,average between 3000 fps and 1500 fps). I haven't directly tested any pointed 210's, but I have pointed some .30 cal 155 grain VLD's,same ogive) and they had an average 3.5% drag reduction,directly correlates to 3.5% BC increase).

3.5% isn't anything to sneeze at. Remember that this BC improvement is coming without any additional weight added. As a result the muzzle velocity doesn't suffer like it would if you 'add' BC by using a heavier bullet.

Pointing bullets helps some shapes/calibers more than others. In general, the smaller calibers stand more to gain from pointing than larger calibers.

-Bryan

 

[TonyR]

Bryan,
Jason Baney discusses some tests by Larry Bartolome and Ken Oehler that showed BC variations within boxes of bullets of between .010 and .040 with an average of .019. Can you talk about the BC variation within boxes of bullets that you have observed? The testing I have done at 1000 yards with some high quality 6mm match bullets points to something very close to the average if I work the reduction of vertical backwards through the EXBAL exterior ballistics program.
Thanks.
Tony

 

[mikecr]

As far as BC in competition,, someone recently compiled 1KBR standing statistics, and it showed undeniably that 30cals did better overall. That is, highest placing percentage by numbers. There were by far more of them, and they still produced higher placing percentages.

Now, this majority of shooters probably didn't arrive there based on 30cal cartridges 'inherent accuracy'. And the rest of the shooters, by majority numbers, are shooting heaviest/cal as hard as they can. Why do you think that is?
Regardless of cal, are heaviest bullets more accurate? More consistent?

No, IT'S ALL ABOUT WINDRIFT

Now, of course there are those anomalies pulled off against the odds. ONCE IN A WHILE.
Not enough to steer many to accept high wind error.
But maybe enough to pull out a second,very accurate) gun in 6br, -if there is no wind whatsoever.

If you consistently shoot 1/2moa in 1KBR, you consistently place well, Right? 5" groups..
Is there anyone out there shooting 1/4moa at 1K -consistently?
Is there really anyone who would step to that line with a gun shooting OVER 1/2moa under no wind conditions?

I'm thinking every gun on that line is accurate enough to win. So the devil's sorting amounts to hold-off error.
And anamolies aside, the winners are best prepared for it.

I don't compete. But it is just obvious to me that competitors shoot High BC for reasons unrelated to accuracy of their guns. They are playing to win.

 

[Bryan Litz Ballistics]

Tony,

My test procedure and data reduction are designed to establish the BC for a particular bullet type over a certain velocity range from a group of shots. Measurement of the average BC for a given bullet is repeatable within +/- 1%. However, the BC of each shot is not measured within +/- 1%. I've always attributed most of the shot to shot variation to random measurement uncertainty, and not actual variation in bullet BC.

The BC variation between lots of bullets,any brand) can be quite significant, like +/- 3%,+/- 0.015 for bullets with a BC of 0.500), although it's not usually that much.

I really don't think that much variation exists within a single box. My estimate is that +/- 1% is more likely,+/- 0.005 for bullets with a BC of 0.500)

Consider this: +/- 3% variation in BC corresponds to about +/- 6" shift in POI at 1000 yards,total 12" of vertical), and that's without any consideration to velocity variation or inherent rifle precision.

The +/- 1% variation within a lot will only give you about +/- 2" of vertical at 1000 attributable to BC variation, a total of 4" of vertical.

In other words, I think you can see up to a 12" shift in POI at 1000 yards if you change lots of bullets and happen to go from 'unusually high' to 'unusually low' or vise-versa. However, if this much BC variation existed within a single box, how could you ever shoot a group that's less than 12" tall?

I believe that shot-to-shot variations in measured BC can be quite high, but I attribute that to the resolution of the measurement more than the actual BC.

-Bryan

 

[aJR]

In my testing with hi BC bullets,VLDs) it has been the portion of the bullet just back from the meplat that is the critical area in maintaining low vertical dispersion . If the bullets i have checked are any indication the older design,say like the 200gn SMK ia a lot more consistant than say the 210 VLD style.If you want to spend some time in good conditions at 1000yds,try 2 lots of 10 shot groups,one with the bullets checked = Weight / B to O / Bearing Surface / meplat uniformed and inspected and then the next 2 lots by an additional batching of base to ogive at a diameter of about .200 ins.. This is on my 187s is at.335 thou back down from the meplat,now if the diameter at this point is not the same you will notice 2 things,1 the vertical will increase and 2 the loaded round AOL will vary to a larger degree because the seating cone is pushing the bullet with the bigger dia further into the case .etc..A recent real world test in the US using 2 Oheler 43s over 1000yds,trialing the 210ber/210Smk/ 208 Amax and the 187 BIB showed the least Vertical dispersion /the smallest group and the lowest ES at target to be the 187, placement of the group was not a consideration in this test,coincidence i don't think so..If you have a bullets that leave at 20fps of ES and arrives 1K away at 100 fps then you are to have a battle in a quest for 3inch groups even though in most instances the group will be actually smaller than the ES should allow anyhow ..This is not to say you can't batch all the others to get the vertical down ..What i don't seem to be able to get through to most of the Prone guys over here is that if you have less vertical then not only can the gun group better BUT it will score better too In the thousands of bullets i've shot, the VLDs are flat just harder to reduce the vertical on.. Your mileage may vary,please don't shoot the messenger ..JR..Jeff Rogers

 

[TonyR]

aJR.

I too have found that better vertical increases scores when shooting at a round target. It better because all I know how to do is chase the spotter.

So, if I wanted to use your measurement technique, I would put a 20 caliber insert into my comparator and remeasure the base to ogive dimension then resort accordingly???

Sounds like a great idea.

Thanks.

 

[jb1000br]

G'day Jeff!

Good to see you posting Tony.

Tony, I like your "sorting with the drill gage" idea! Would be interesting to see how some round-robin groups at 1000 separate your batches using the drill bit gage...

Jeff, RE: your "base-to tip at 0.2 diameter" Is this the point where your seater plug indexes, or is this where the end of the core lies on the interior? or something else?

I have overall, seen more consistent improvement in performance with pointing then trimming. But that is just me.

Jeff you are doing awesome things with those BIB's

Bryan - I can't vouch for Larry and Dr. Ken's measuring precision, but it would be interesting to clarify that to more clearly interpret the results. Though, how could one even assess that in the real world?,using other than lab/calculation results)

JB

 

[aJR]

Hi Tony, With whatever bullet dia you use it's best for the seater cone to push on the supported section of the ogive..I measure in from the meplat till i find how deep the core is placed,then make a step diameter accordingly.. This happens to be at .200 on most of the bullets in the 30 cal that i've used.. At about .180 is where i discovered to large differences on the 7mm i tested,this was with the 175SMK and the 180 Ber. The old 168 SMK was just about 100 from 100 perfect..Helping a pal set up for the 210 ber shortly, got some selected good one's from one of your countryman,Thanks again Phil),but as they stabilize in a 12 twist i don't think they are a VLD in the same light as the 180 7mm bullet is so i hopeing it will not be as critical And yes your right no one shoots at square targets,their all round,no matter what discipline you follow..JR..Jeff Rogers

aJR.

I too have found that better vertical increases scores when shooting at a round target. It better because all I know how to do is chase the spotter.

So, if I wanted to use your measurement technique, I would put a 20 caliber insert into my comparator and remeasure the base to ogive dimension then resort accordingly???

Sounds like a great idea.

Thanks.